The proposed research can be divided into three categories: 1) Improvements in the design and fabrication of the existing total artificial heart (TAH): The design has been modified to allow increased maximum cardiac ouput to approximately 15 1/min without any appreciable increase in size. Smooth surface materials such as Polyether-type polyurethane and Avcothane (copolymer of silicone rubber and polyurethane) will be used in the new heart. 2) Critical evaluation of the performance and durability of the prosthesis and newly designed movable control-driving unit by in vitro and in vivo testing: The heart powered by the new control and driving unit will be tested in our mock- circulatory system. Following this evaluation, in vivo testing of the combination will be performed. 3) Pathophysiological studies in long- term survivals: Major emphasis will be given to studies on anemia, body fluid balance, and difference in response to exercise between the natural heart and TAH. Calorimetry and cardiovascular drug tests will be performed.